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Polarization measurements are usually considered as the most difficultchallenge for the QCD description of quarkonium production. In fact, globaldata fits for the determination of the non-perturbative parameters ofbound-state formation traditionally exclude polarization observables and usethem as a posteriori verifications of the predictions, with perplexing results.With a change of perspective, we move polarization data to the centre of thestudy, advocating that they actually provide the strongest fundamentalindications about the production mechanisms, even before we explicitly considerperturbative calculations.  Considering psi(2S) and Y(3S) measurements from LHC experiments andstate-of-the-art NLO short-distance calculations in the framework ofnon-relativistic QCD factorization (NRQCD), we perform a search for a kinematicdomain where the polarizations can be correctly reproduced together with thecross sections, by systematically scanning the phase space and accuratelytreating the experimental uncertainties. This strategy provides astraightforward solution to the "quarkonium polarization puzzle" and reassuringsigns that the theoretical framework is reliable. At the same time, the resultsexpose unexpected hierarchies in the non-perturbative NRQCD parameters, thatopen new paths towards the understanding of bound-state formation in QCD.

Quarkonium production in the LHC era: a polarized perspective